Such a massage machine is described in, for example, Japanese Patent Application Publication No. 2005-152260 issued Jun. 16, 2005. This machine (hereinafter referred to as a “first prior art”) uses an electric reclining mechanism of a backrest to obtain a stretch (extension) effect on the user's arms and shoulders. That is, the first prior art swells upper and lower airbags located at each of left and right armrests to hold each hand and forearm of the user with each upper and lower airbags, and moves the backrest into an end position from a start position to lean the upper part of the user's body backward. The start position is a sloping position, and the end position is a sloping position that has an inclination larger than the start position with respect to the vertical direction. In case of a first operational example, the first prior art moves the backrest into the end position while swelling the airbags of the armrests; returns the backrest to the start position after the airbags finish swelling; and shrinks the airbags after holding each swell condition of the airbags for a specified time. In case of a second operational example, the first prior art swells the airbags of the armrests; moves the backrest into the end position after the airbags finish swelling; and returns the backrest to the start position while shrinking the airbags after holding each swell condition of the airbags for a specified time. However, in this first prior art, there is an issue that the two sets of upper and lower airbags restrain the user's arms simultaneously.
Another massage machine described in Japanese Patent Application Publication No. 2005-177278 issued Jul. 7, 2005 can solve the issue. This massage machine (hereinafter referred to as a “second prior art”) also swells upper and lower airbags located at each of left and right armrests to hold each hand and forearm of the user with each upper and lower airbags, and moves the backrest into an end position from a start position to lean the upper part of the user's body backward. At this point, the second prior art adjusts holding strength by upper and lower airbags located at one of the left and right armrests so that the user can take the corresponding arm off the upper and lower airbags. Therefore, the second prior art can prevent two sets of upper and lower airbags from restraining the user's arms simultaneously.
However, the second prior art decreases holding strength by upper and lower airbags located at one of the left and right armrests and accordingly cannot hold the user's corresponding hand and forearm surely.